Hip replacement surgery was first performed in 1960 and is considered to be one of the most important surgical advances of the century. Since then improvements in joint replacement, surgical techniques and technology have increased the effectiveness of this surgery. Today, more than 172,221 total hip replacements are performed each year in the United States according to the American Academy of Orthopedic Surgeons. It has also been reported that over 250,000 Americans undergo knee replacement surgeries each year. This surgical procedure was first performed in 1968 and typically relieves knee pain and restores joint function.
Today orthopedists and researchers recognize that placing some force on healing bones of the lower extremity following surgery, fracture or replacement stimulates bone healing. However, excessive force may result in the delayed healing or malunion of the bone. Therefore, for each fracture and location of fracture an optimal and measurable range of force should be placed across the fracture to maximize bone healing. Further, the peak force should be monitored in each gait cycle to be certain that it does not exceed a maximum limit prescribed by a physician. When physicians provide written orders to physical therapists regarding ambulatory training, they may prescribe “partial weight bearing status”. Such instructions are vague and may result in too much or too little force being applied to the affected limb. This may result in damage to the limb or less than optimal healing. Accordingly, there is a need for monitoring weight bearing on a limb during movement of the body.
An orthopedic weight monitor for detecting weight bearing forces on a lower extremity for orthopedic purposes is disclosed in a U.S. Pat. No. 5,253,654 of Thomas et al. As described therein a flexible pad is shaped to conform to the bottom of a foot for placement inside of a shoe or cast. The pad has a heel portion for placement beneath the heel of a user, a sensor is incased within the heel portion of a pad to be located beneath the heel of the user. An electronic module is remotely positioned from the sensor to receive signals from the sensor.
A more recent development is shown in a U.S. Patent of Wanderman et al., U.S. Pat. No. 5,511,561 that discloses a gait cycle force monitor to detect the amount of force translated through a patient's heel in each gait cycle. The foot-pad has a tactile force sensor, means to translate a force applied to the sensor, a comparator and an annunciater. The comparator which can be analog or microprocessor controlled has a set point and an amplifier that is activated when the voltage from the sensor exceeds the set point. The piezo-electric annunciater is driven by the amplifier to warn the patient that excessive force is being translated through the heel.
Notwithstanding the above it is presently believed that there is a need and a potential commercial market for an improved gait training device and method in accordance with the present invention. There should be a need and commercial market for such devices that provide dynamic measure and weight distribution between the patient's lower extremities. The devices in accordance with the present invention also measure the weight under each heel in each gait, and may provide a more natural gait during testing. Further, it is presently believed that such devices may be particularly applicable for testing and treating disorders and or injuries to the lower spine.
In addition to the above, the devices and methods in accordance with the present invention can be manufactured and sold at a competitive price, are durable and easily used by physical therapists.